merge revision(s) 39349,39374: [Backport #7886]

	* file.c (rb_group_member): get rid of NGROUPS dependency.
	  [Bug #7886] [ruby-core:52537]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@39588 b2dd03c8-39d4-4d8f-98ff-823fe69b080e